geosciences Article Ore Petrography Using Optical Image Analysis: Application to Zaruma-Portovelo Deposit (Ecuador) Edgar Berrezueta 1,*, Berta Ordóñez-Casado 1, Wilson Bonilla 2, Richard Banda 3, Ricardo Castroviejo 4, Paul Carrión 5 and Stalin Puglla 6 1 Instituto Geológico y Minero de España, C/Matemático Pedrayes, 25, Oviedo 33005, Spain;
[email protected] 2 Consultor-Auditor Minero Freelance, Piñas 070401, Ecuador;
[email protected] 3 Universidad de Guayaquil, Av. Raúl Gómez Lince s/n y Av. Juan Tanca Marengo, Guayaquil 090612, Ecuador;
[email protected] 4 Universidad Politécnica de Madrid. España, C/Ríos Rosas, 21, Madrid 28003, Spain;
[email protected] 5 Escuela Superior Politécnica del Litoral, Campus Prosperina Espol, Guayaquil 090903, Ecuador;
[email protected] 6 Compañía Minera PL S.A., Zaruma 070301,Ecuador;
[email protected] * Correspondence:
[email protected]; Tel.: +34-609-381-623 Academic Editor: Antonio Acosta-Vigil Received: 19 April 2016; Accepted: 12 June 2016; Published: 21 June 2016 Abstract: Optical image analysis (OIA) supporting microscopic observation can be applied to improve ore mineral characterization of ore deposits, providing accurate and representative numerical support to petrographic studies, on the polished section scale. In this paper, we present an experimental application of an automated mineral quantification process on polished sections from Zaruma-Portovelo intermediate sulfidation epithermal deposit (Ecuador) using multispectral and color images. Minerals under study were gold, sphalerite, chalcopyrite, galena, pyrite, pyrrhotite, bornite, hematite, chalcocite, pentlandite, covellite, tetrahedrite and native bismuth. The aim of the study was to quantify the ore minerals visible in polished section through OIA and, mainly, to show a detailed description of the methodology implemented.